This invention relates to metal-to-metal seals and metal-to-metal seals in combination with elastomeric seals, but is specifically related to wellhead systems with such seal assemblies, often referred to as pack-off assemblies comprising such seals, for sealing the annular space, often referred to as an annulus or gland, between a wellhead casing hanger and the surrounding cylindrical wall of a wellhead.
As stated, another way, the metal-to-metal seals with or without elastomeric seals are disclosed herein in connection with wellhead systems as part of their pack-off assemblies, but such seals may also be used to seal any annulus between tubular body members.
The U.S. Pat. No. 3,468,558 and later patents such as U.S. Pat. No. 3,871,449 explain the operation and purpose of pack-off assemblies in wellheads as well as various ways of running and setting the pack-off, i.e., sealing the annulus.
These patents also show different types of pack-offs and the U.S. Pat. Nos. 3,797,864 and 4,521,040 illustrate more recent pack-offs which comprise an elastomeric ring interposed between two metallic seal rings with each metallic seal ring having a pair of lips extending toward the elastomeric material. By the compression of the elastomeric material, the lips are forced outwardly towards the surrounding walls to thus seal the annulus with both the elastomeric material and metal.